Cells producing antibody compositions with increased antibody dependent cytotoxic activity

An isolated fucosyltransferase knock-out host cell wherein when a gene encoding an antibody molecule is introduced in to said host cell, said host cell produces an antibody composition comprising the antibody molecule,

• said host cell being a mammalian cell,
• said antibody molecule comprising a Fc region comprising complex N-glycoside-linked sugar chains bound to the Fc region,
• said sugar chains comprising a reducing end which contains an N-acetylglucosamine, wherein the sugar chains do not contain fucose bound to the 6 position of N-acetylglucosamine in the reducing end of the sugar chains.